The navigation aid system assists the crew in programming the flight plan before take-off and in monitoring the path of the flight plan from take-off through to landing. Its assistance in programming the flight plan consists on the one hand in plotting, in the horizontal and vertical planes, a path sketch formed by a succession of waypoints associated with various clearances such as altitude, speed, heading or others, and on the other hand in computing, also in the horizontal and vertical planes, the path that the aircraft will follow to complete its mission.
When preparing the programming of the flight plan, the crew inputs into the navigation aid system, explicitly or implicitly, the geographic coordinates of the waypoints and their associated clearances, and obtains from the navigation aid system a path sketch and a flight path. The path is made up of a chain of segments linking the waypoints two by two from the starting point through to the destination point, and arcs of circle providing the heading transitions between segment at the waypoints. The path sketch and the path are displayed on a navigation screen to enable the crew to check their relevance.
Before take-off, or during the flight, the air traffic control (ATC) authority sends the crew the clearance execution orders, via the navigation aid system. These are confirmations of the clearances scheduled in the flight plan, or changes of clearances.
Some of these orders have no impact on the flight path, such as, for example, an order concerning a change of communication frequency. Others require the flight path to be modified; among these, there are orders with immediate execution and orders with deferred execution.
When an immediate execution order is received by the navigation aid system, the latter modifies the flight plan according to this order and immediately recomputes the new modified flight path, communicates it to the crew and to ATC, and sends the clearance associated with the order to the aircraft guidance device.
A deferred execution order comprises a condition; when the condition is satisfied, the clearance must then be executed.
When a deferred execution order is received by the navigation aid system, the latter monitors the triggering of the condition and, immediately the condition is satisfied, it processes the order as an immediate order: it modifies the flight plan according to this order, recomputes the new flight path, communicates it to the crew and to ATC, and transmits the clearance to the guidance device. However, there is no anticipation: neither ATC nor the crew know the new flight path until it is operational.
The aim of the invention is to overcome this drawback.
The principle of the invention is to estimate where the condition will be satisfied, and to compute, anticipatively, the new flight path modified by the order.